What are prisms in optical devices (binoculars/monoculars) and what is the difference between K9, BAK4 and roof prisms?
are characterized by a distinctive Z-shaped design that allows for a longer optical path and greater image depth perception. They are typically made from a type of glass called BK7, which has a lower refractive index than other types of glass, making it less expensive to manufacture.
K9 is another type of glass that is sometimes used in binoculars and monoculars. It has a lower refractive index than BAK4 and BK7 glass, making it less expensive, but also less effective at correcting the image and providing a clear and bright view.